US 2007/0275036 Al describes that follistatin is known to be present in fertilized avian eggs and is biologically active to increase muscle mass and to facilitate muscle regeneration in humans. Whereas the pasteurization of liquid egg yolk is shown to inactivate the biological activity of follistatin contained therein, it is described that freeze-dried emulsified egg yolk can be irradiated e.g. by gamma radiation or by an electron beam for preservation without inactivating follistatin.